/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
 * Copyright 2015 Pelican Mapping
 * http://osgearth.org
 *
 * osgEarth is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 */

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#ifndef OSGEARTH_SHADER_LOADER_H
#define OSGEARTH_SHADER_LOADER_H 1

#include <VBF_3DMap/VBF_Terrain/Common.h>
#include <VBF_Engine/VBF_SGDB/Options>
#include <map>

namespace osgEarth
{
    class VirtualProgram;

    /**
     * Functions to help load shader code.
     */
    class OSGEARTH_EXPORT ShaderPackage
    {
    public:
        /**
         * Adds a function from this package to the VirtualProgram.
         */
        bool load(
            VirtualProgram*       vp,
            const std::string&    filename,
            const osgDB::Options* dbOptions =0L ) const;

        /**
         * Removes a function loaded by load from the VirtualProgram.
         */
        bool unload(
            VirtualProgram*       vp,
            const std::string&    filename,
            const osgDB::Options* dbOptions =0L ) const;

        /**
         * Adds all the functions in this package to the VirtualProgram.
         */
        bool loadAll(
            VirtualProgram*       vp,
            const osgDB::Options* dbOptions =0L ) const;

        /**
         * Removes all the functions in this package from the VirtualProgram.
         */
        bool unloadAll(
            VirtualProgram*       vp,
            const osgDB::Options* dbOptions =0L ) const;

        /**
         * Defs or undefs a GLSL #define proprocessor macro.
         * Don't include the "#" in the defineName.
         */
        void define(
            const std::string& defineName,
            bool               defOrUndef);

        /**
         * Replaces the specified string with another string in the loaded
         * shader source. Nested replacements are not supported.
         */
        void replace(
            const std::string& pattern,
            const std::string& value);

    public:
        typedef std::map<std::string, std::string> SourceMap;
        typedef std::map<std::string, std::string> ReplaceMap;
        typedef std::map<std::string, bool>        DefineMap;

        const SourceMap& context() const { return _sources; }

        void add(const std::string& filename, const std::string& inlineSource) {
            _sources[filename] = inlineSource; }


    protected:        
        SourceMap _sources;
        DefineMap _defines;
        ReplaceMap _replaces;
        friend class ShaderLoader;
    };

    /**
     * Base class for local shader file/source pairs.
     */
    class OSGEARTH_EXPORT ShaderLoader
    {
    public:
        /**
         * Loads shader source from the specified filename, and calls 
         * setFunction() on the virtual program to install the shader.
         * The shader much include #pragma definitions for both its
         * entry point and its location, e.g.:
         *
         *   #pragma vp_entryPoint "oe_my_shader"
         *   #pargma vp_location   "VERTEX_VIEW"
         */
        static bool load(
            VirtualProgram*       vp,
            const std::string&    filename,
            const ShaderPackage&  package,
            const osgDB::Options* dbOptions =0L );

        /**
         * Removes a function loaded by load from the VirtualProgram.
         */
        static bool unload(
            VirtualProgram*       vp,
            const std::string&    filename,
            const ShaderPackage&  package,
            const osgDB::Options* dbOptions =0L );

        /**
         * Loads shader source from the specified filename. If the
         * file can't be found in the OSG file path, use the source
         * provided in backupSource.
         */
        static std::string load(
            const std::string&    filename,
            const std::string&    backupSource,
            const osgDB::Options* dbOptions =0L );

        static std::string load(
            const std::string&    filename,
            const ShaderPackage&  package,
            const osgDB::Options* dbOptions =0L );
    };

} // namespace osgEarth

#endif // OSGEARTH_SHADER_LOADER

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